Glycerol dichlorohydrin



Patented Apr. 30, 1940 UNITED STATES PATENT OFFICE GLYCEROL DICHLOROHYDRIN gan No Drawing. Application September 10, 1936, Serial No. 100,211

10 Claims.

This invention concerns the use of organic solvents in the purification of glycerol dichlorohydrin.

When glycerol is reacted with hydrogen chloride in the presence of a suitable catalyst such as acetic acid to form glycerol dichlorohydrin and 2 molecules of water, the known processes either allow the water of reaction to accumulate in the reaction zone, or drive the water out of the reaction mixture by conducting the reaction at elevated temperatures, 1. e., approximately 120 C. or higher. If the water of reaction be allowed to accumulate in the process, there is obtained on fractional distillation of the mixed reaction product a substantial fraction composed of water, hydrogen chloride, acetic acid, and glycerol dichlorohydrin, while if water is distilled from the reaction zone at elevated temperatures during the reaction, considerable quantities of glycerol dichlorohydrin, acetic acid, and hydrogen chlo ride are carried out therewith to form a similar corrosive mixture. Losses of glycerol dichlorohydrin in the above aqueous fractions are considerable, and the literature describesscveral methods for the partial recovery of dichlorohydrin therefrom, which involve complicated distillation methods and/or neutralization of said acid fractions with soda ash or similar alkalies. It has been found impossible to separate more than a small portion of dissolved dichlorohydrin product from these solutions by distillation, and while neutralization of the corrosive mixtures with soda ash, etc., accomplishes a better separation than does distillation, glycerol dichlorohydrin has a considerable solubility in water and salt solutions, and the method fails in recovery of a substantial portion of the desired product. Furthermore, neither of the above methods is particularly adapted to produce an anhydrous product, considerable amounts of water being present in glycerol dichlorohydrin recovered from aqueous hydrogen chloride solutions thereby.

We have discovered that by extracting the above-described glycerol dichlorohydrin-containing acid iractions with a suitable organic solvent the major proportion of the desired dichlorohydrin product may be recovered from such corrosive mixtures and, furthermore, that fractional distillation of the extract 30 obtained yields essentially anhydrous glycerol dichlorohydrin. The essential characteristics of a suitable organic solvent", as the term is employed in the specification and claims of this application, are that (1) it have a high extraction coeflicient for glycerol dichlorohydrin in aqueous acid solution,

that is, the solubility of glycerol dichlorohydrin in the solvent must be such that said solvent is capable of conveniently extracting the major proportion of glycerol dichlorohydrin from solution in water or aqueous hydrochloric acid; (2) it must not extract appreciable quantities of hydrochloric acid from the treated corrosive mixtures; (3) it must be relatively immiscible with water: (4) it must be readily separable from the extracted aqueous solution as by decantation, and from glycerol dichlorohydrin as by distillation; and i 5) it must be inert, that is, must not contain groups which tend to react with glycerol dichlorohydrin and hydrochloric acid or be hydrolyzed during the extracting and distilling steps.

In carrying out our process the water or aqueous hydrochloric acid solution of glycerol dichlorohydrin, which may or may not contain dissolved acetic acid or other reaction catalyst, is intimately contacted with asuitable organic solvent, the resulting mixture allowed to layer out,

and the glycerol dichlorohydrin-containing'soivent solutionseparated from the aqueous layer. If necessary, several extractions of the aqueous glycerol dichlorohydrin solution may be made,

after which the various extracts may conveniently be combined and the glycerol dichlorohydrin separated therefrom. by fractional distillation. Small amounts of water present in such combined extracts are removed therefrom as a steam dis tillate along with portions of the solvent employed during the first stages of the fractionation, the glycerol dichlorohydrin being recovered in substantially anhydrous form as either a higher or lower boiling fraction, depending upon the boiling point of the organic solvent employed. If desired, the extract may be treated with small amounts of sodium carbonate or other suitable alkaline material prior to the distillation step to remove traces of acetic acid and/or hydrochloric acid which may be present in said extract.

The following examples illustrate the use of certain representative organic solvents in the carrying out of our invention but are not to be construed as limiting the same:

Example 1 38.4 pounds of glycerol and 1.75 pounds of glacial acetic acid were mixed together in a glass reactor and gaseous hydrogen chloride slow ly introduced thereinto, the reaction temperature being maintained between C. and C. Water formed in the reaction continuously distilled from the reaction zone along with portions oi the glycerol dichlorohydrin product, acetic acid catalyst, and hydrogen chloride, which mixture was condensed and collected as an acid fraction. At the endof 56 hours the formation of water had substantially ceased and analysis of an aliquot portionof the reaction mixture indicated an approximately theoretical chlorine content. The 38.1 pounds of crude glycerol dichlorohydrin product remaining in the reaction flask was then fractionally distilled under reduced pressure whereby there was obtained 0.3 pound of a low boiling aqueous acid fraction, 31.0 pounds of substantially pure glycerol dichlorohydrin, 3.2 pounds of glycerol monochlorohydrin and 3.6 pounds of high-boiling residue. The 31.0 pounds of desired product represented a yield of only 57.5 per cent of theoretical based on the glycerol used as a starting material.

The 30.9 pounds of acid fraction recovered as a distillate from the reaction zone during the hydrogen chloride addition thereto was extracted three times with ethylene chloride. Each extraction required between 6 and 8 pounds of solvent and the total weight of ethylene chloride employed was 20.5 pounds. The extracts so obtained were combined and fractionally distilled whereby an additional 8.1 pounds of substantially anhydrous glycerol dichlorohydrin was recovered. The total yield of product was, therefore, 39.1 pounds of glycerol dichlorohydrin, representing a theoretical yield of 72.5 per cent. 20.25 pounds, approximately 99 per cent, of the ethylene chloride used in the extraction was recovered and reutilized in subsequent runs.

Example 2 334 grams of an aqueous acid fraction containing 83.5 grams of glycerol dichlorohydrin and 83.5 grams of dissolved hydrogen chloride was extracted three times with di-normal-butyl ether. 79 grams of ether was employed in the first extraction and removed 58 grams of glycerol dichlorohydrin from the acid solution. The second extraction was made with 78 grams of ether and separated 13 grams of desired product. The third extraction employed 86.5 grams of di-butyl ether and recovered an additional 10 grams of glycerol dichlorohydrin. The total recovery of desired product was, therefore, 81 grams out of a possible 83.5 or 97 per cent of theory.

Example 3 In a similar manner 253 grams of an acid fraction containing 63.2 grams of dissolved glycerol dichlorohydrin and 63.2 grams of hydrogen chloride was successively extracted with 151.5, 145.5, and 149.5 grams of 1,1,2-trichloroethane whereby 28.2, 15.2, and 6.2 grams respectively of dichlorohydrin product was removed from aqueous solution. Fractional distillation of the combined extracts resulted in the isolation of-49.6 grams of substantially anhydrous glycerol dichlorohydrin which represents a recovery of 78.5 per cent of theory.

Example 4 An acid fraction comprising 49.5 grams of glycerol dichlorohydrin and 148.5 grams of a 33% per cent aqueous hydrochloric acid solution was subjected to three extractions with ethylene chloride. The 126.0, 122.0, and 124.5 gram portions of solvent employed in the, extraction removed 23.0, 11.5, and 5.0 grams of dichlorohydrin product respectively from the aqueous solution. Combination of the above extracts and fractional distillation under reduced pressure resulted in the isolation of 39.5 grams of substantially anhydrous and acid-free glycerol dichlorohydrin which represents a recovery of 80 per cent of theoretical.

Example 5 Extraction of 200 grams of an acid fraction consisting essentially of 50 grams of glycerol dichlorohydrin and 150 grams of 33 V per cent hydrochloric acid with 115.5, 119.0, and 108.5 gram portions of propylene chloride and fractional distillation of the combined extracts resulted in the recovery of 39.2 grams of desired product or 78.4 per cent of theory.

While the foregoing examples describe the multiple extraction of acid fractions to recover glycerol dichlorohydrin therefrom, in plant operation the amount of extraction solvent required may be considerably reduced by subjecting the acid fraction to continuous extraction. In this modification of procedure the acid fraction is extracted with a relatively small volume of solvent, small portions of which are continuously withdrawn from the extraction zone into a suitablefractionation apparatus wherein the low boiling solvent and traces of water present in the extract are distilled off and returned to the extraction zone, glycerol dichlorohydrin being retained in the body of the distilling apparatus as a residue. When no additional glycerol dichlorohydrin can be removed from the aqueous acid fraction, the extraction operation is suspended and the accumulated still residue of glycerol dichlorohydrin product is fractionated to obtain the desired compound in substantially pure form. In plant operation employing ethylene chloride as the solvent, an aqueous acid fraction originally containing 25 per cent by weight of glycerol dichlorohydrin, was found after extraction to contain only 3 per cent by weight .of said compound dissolved therein.

Among other solvents which have been found satisfactory as extractants in our process are diisopropyl ether, butylene chloride, the chloroethyl ethers, etc. If desired, mixtures of two or more solvents may be employed, for example, dibutyl ether-ethylene chloride, dipropyl etherethylene chloride mixtures, etc. Such combinations of'solvents are of particular value where it is desired (1) to reduce fire hazard and flammability of the extraction mixture, and (2) to attain some particular specific gravity for the extracting solvent in order to facilitate separation of said extractant from the aqueous acid fraction.

Other modes of applying the principle of our invention may be employed instead of those explained, change being made as regards the methods herein disclosed, providing the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention:

1. In the recovery of glycerol dichlorohydrin from an aqueous solution comprising the same, the step which consists in extracting said solution with di-normal-butyl ether.

2. In the recovery 01' glycerol dichlorohydrin from an aqueous solution comprising the same, the steps which consist in extracting said solution with di-normal-butyl ether and thereafter separating the glycerol dichlorohydrin from the di-butyl ether by fractional distillation.

3. In the recovery of glycerol dichlorohydrin from an aqueous solution comprising the same.

the steps which consist in removing the major portion of the dissolved glycerol dichlorohy drin from said solution by extracting the same with di-normal-butyl ether and thereafter fractionally distilling the extract to recover the glycerol dichlorohydrin.

4. In the extraction of glycerol dichlorohydrin from an aqueous hydrochloric acid solution comprising the same, the steps which consist in intimately contacting said solution with (ii-normalbutyl ether, withdrawing the resulting solventglycerol dichlorohydrin extract from the extraction zone, and thereafter removing residual water and di-butyl ether from said extract by fractional distillation whereby glycerol dichlorohydrin is obtained in substantially anhydrous condition.

5. In the recovery of glycerol dichlorohydrin from an aqueous solution comprising the same, the step which consists of extracting said solution with an inert water-immiscible organic solvent, selected from the group consisting of dialkyl ethers and chloro-di-alkyl ethers, wherein each alkyl group contains not more than 4 carbon atoms.

6. In the recovery of glycerol dichlorohydrin from an aqueous solution comprising the same, the steps which consist of extracting said solution with an inert water-immiscible organic solvent selected from the group consisting of dialkyl ethers and chloro-di-alkyl ethers, wherein each alkyl group contains not more than 4 carbon atoms, and thereafter separating the glycerol dichlorohydrin from the organic solvent by fractional distillation.

7. In the recovery of glycerol dichlorohydrin from an aqueous hydrochloric acid solution comprising the same, the step which consists of extracting said solution with an inert water-immiscible organic solvent selected from the group consisting of di-alkyl ethers and chloro-di-alkyl ethers, wherein each alkyl group contains not more than four carbon atoms.

8. In the recovery of glycerol dichlorohydrin from an aqueous hydrochloric acid solution comprising the same, the steps which consist of extracting said solution with an inertwater-irnmiscible organic solvent selected from the group consisting of di-alkyl ethers and chloro-di-alkyl ethers, wherein each alkyl group contains not more than four carbon atoms, and thereafter separating the glycerol dichlorohydrin from the organic solvent by fractional distillation.

9. In the recovery of glycerol dichlorohydrin from an aqueous solution comprising the same, the steps which consist of separating the major portion of the dissolved glycerol dichlorohydrin from said solution by extracting the same with an inert water-immiscible organic solvent selected from the group consisting of di-alkyl ethers and chloro-di-alkyl ethers, wherein each alkyl group contains not more than 4 carbon atoms, and thereafter fractionally distilling the extract to obtain the glycerol dichlorohydrin.

10. In the extraction of glycerol dichlorohydrin from an aqueous hydrochloric acid solution comprising the same, the steps which consist of intimately contacting said solution with an inert water-immiscible organic solvent selected from the group consisting of di-alkyl ethers and chlorodi-alkyi ethers, wherein each alkyl group contains not more than 4 carbon atoms, withdrawing the resulting solvent-glycerol dichlorohydrin solution from the extraction zone, and thereafter removing residual water and organic solvent from said extract by fractional distillation whereby giycerol dichlorohydrin is obtained in substantially anhydrous condition.

EDGAR C. BRI'I'ION. HAROLD R. SLAGH. 

